I guess, in the sense that anyone could be not wrong making nearly any claim about this service as we know it now.
Nintendo isn't typically the kind of entity to use insanely absurd pedantics.
The only Nintendo game that is online-only that I'm aware of is Mario Run. It's an UNBELIVABLY shitty thing which I hate, but that's a phone game. It's a significant distinction.
Fire Emblem Heroes and Miitomo also are, but both are mobile-only too. Nintendo Badge Arcade is the only online-only Nintendo title on a Nintendo system that I know of.